This application claims priority to Japanese Patent Application No. 2002-57236, disclosure of which is incorporated herein by reference.
The present invention relates to a glass ceramic dielectric material suitable for production of a microwave circuit component.
As a material of a circuit component, such as a ceramic substrate, to which ICs or LSIs are mounted at a high density, use is made of an alumina ceramic material and a glass ceramic material including glass powder and ceramic powder. In particular, the glass ceramic material can be fired at a temperature not higher than 1000° C. although it is inferior in mechanical strength to the alumina ceramic material. Therefore, the glass ceramic material is advantageous in that the material can be co-fired with Ag, Cu, or the like low in conductor resistance.
In recent years, remarkable development has been achieved in the fields of a mobile communication apparatus, such as a mobile telephone and a personal radio equipment, and a new media apparatus used in a new media, such as satellite broadcasting, satellite communication, and CATV. In the mobile communication apparatus and the new media apparatus, a microwave circuit component is used. It is required that the microwave circuit component is made of a material low in dielectric loss in a high-frequency region not lower than 0.1 GHz.
Sometimes, the microwave circuit component itself is required to serve as a resonator. In this case, the material of the microwave circuit component is required to have temperature stability, i.e., to be unchanged in resonance frequency depending upon the temperature.
For example, Japanese Unexamined Patent Publication No. H10-120436 (JP 10-120436 A) proposes a glass ceramic material which precipitates diopside crystals. By the use of the glass ceramic material, it is possible to obtain a sintered product low in dielectric loss in the high-frequency region. However, the glass ceramic material has a dielectric constant between 6 and 8, which is lower than that of alumina. In addition, the glass ceramic material is inferior in temperature stability because a temperature coefficient of the resonance frequency is −65 ppm/° C.